Some tool machines, for example, the lathes, have a turret for the mounting of one or more rotating tools, the rotating tools are controlled by an actuating motor in such a way as to process a piece on the tool machine.
In some known lathes, the turret has a turning block mounted on a fixed head of it, and a plurality of tools, chosen among rotating tools and other processing tools, radially supported on the turning block.
When the turning block is rotated around its axis, one of the supported instruments (for example, a rotating tool) is moved to the processing position, at this point the motor is moved in such a way as to actuate the turning tool and rotate it around its axis in such a way as to process the piece on the machine.
The actuating power or the actuating motor torque are transmitted to the rotating tool by a power transmission body such as for example a belt, conical gears and bearings.
The document US2004/0103510 describes a turret of the aforementioned type provided with an actuating motor positioned in a rotating drum. The actuating motor is directly connected to the rotating tool mounted on the turret in such a way as to rotate it through a coupling mechanism (in other words, the power is transmitted by means of a mechanical group of power transmission).
The patent application JP2003-251505, describes instead a turret for a lathe suitable for transmitting the driving power from an actuating motor to a rotating tool mounted on the turret. The power is transmitted through a transmission group comprising conical gears and bearings. The turret comprises a hollow rotating drum which houses within it the transmission group.
The Applicant has noted that in turrets for lathes of conventional type, such as the one described in JP2003-251505, the actuating motor is positioned in a considerably distant position with respect to the rotating tool, consequently the mechanical group of transmission for transmitting the movement from the motor to the rotating tool must necessarily have a complex structure.
The Applicant has further noted that as of today the movement of tools mounted to on turrets for lathes takes place with belt transmissions and gears. In other words, tools are mounted on devices completely independent from the actuating motor. For the rotation of tool, these devices are coupled to the actuating motor with belt transmission, gears or through special joints.
These transmission systems negatively affect processing precisions, are very is complex and still do not proof to be particularly efficient and quick.
The document DE 39 08 586 A1 shows a turret for tool machine wherein a tool holder is indirectly actuated by an electrical spindle by means of an indirect engagement. In details, although this document does not show the presence of belt or gear actuating means, it shows anyway the presence of a friction discoidal joint, interposed between the electrical spindle and the tool holder. In said friction discoidal joint is introduced a plurality of tips of a pair of pins which come out from the electrical spindle itself. The Applicant has noted that also the solution shown in the German document is characterized by the drawback that the joint negatively affects the processing precisions and complicates the realization of the machine, particularly making critical the transmission of high torques and the works at high speeds.
As a matter of fact, the engagement of the discoidal joint takes place thanks to a pair of pins which come out from the shaft of the electrical spindle, which engage on respective recesses in the joint itself. The pins are thin and thus subject to the fracture risk. Furthermore, the movement transmission takes place by means of a joint which is non coaxial with the rotation axis of the electrical spindle; this weakens the coupling because in case of clearances between the pins and the diameter of the spins themselves, the high distance from the rotation center creates not negligible reciprocal angular rotations between the pin and the joint, capable also of breaking the pin itself.
From the document DE10 2005 033 890 is known a turret for tool machines wherein the movement transfer between the motor shaft and the tool holder takes place with an intermediate joint interposed between the tool holder and the shaft itself, once more with an indirect engagement. In this last document, the motor is fixed and it cannot move axially. This makes the coupling change between the shaft of the electrical spindle and the tool holder more complicated.
The same configuration can also be found in document EP 1642 676, characterized by a transfer of rotation movement between the rotating shaft of the electrical spindle and the tool holder by means of a joint interposed between them too, also in this case realizing an indirect mechanical engagement.
In addition, in all the documents above described, the tool holders are solidly connected with the support which turns with respect to the spindle. Consequently, during the working phase, the various working forces are supported by the tool holders which turn on bearing which are in turn constrained to the support and clipped to the wheel.
The electrical spindle, transmits then only the rotating movement to the various tool holders with various transmission systems.
With this system, the zero point of each tool will not always be the same: it depends on the precision of production of the wheel itself, such as distances and angular divisions, particularly if the offset of the effective coupling between the shaft of the spindle and the pins becomes more and more accentuated.
With this system, the angular position of the tool cannot be controlled.
Therefore, the Applicant has found the need for providing a turret for tool machines capable of solving the drawbacks of the background art.
The Applicant has noted that the problems above described can be solved with a turret wherein the actuation of the rotating tool takes place directly, without the interposition of mechanical transmissions between the actuating motor and the tool.